<html>
<body>
<p id="demo">Click the button to display a specified date after changing the day of the month.</p>
<button onclick="myFunction()">Try it</button>
<script>
function myFunction()
{
var d = new Date("July 21, 1983 01:15:00");
d.setDate(15);
var x = document.getElementById("demo");
x.innerHTML=d;
}
</script>
</body>
</html>